Abstract

Purpose

The circumventricular organs (CVOs) occupy seven midline locations around the ventricles. They contain specialized ependymal cells called tanycytes and have an incomplete blood–brain barrier (BBB). We hypothesized that appearances of the lesser known CVOs on contrast-enhanced MRI might lead to confusion in image interpretation whereby they might be mistaken for pathology-related abnormal contrast enhancement. We therefore assessed the normal appearances and prevalence of contrast enhancement of the CVOs on routine clinical brain MRI and reviewed the functional anatomy of the CVOs.

Results

The frequency of contrast enhancement of the seven CVOs was as follows: ME in 100 %, NH in 96 %, PG in 84 %, SFO in 1 %, OVLT in 34 %, SCO in 0 %, and AP in 2 %.

Conclusions

The main CVOs (ME, NH, and PG) are well known and appreciated on brain imaging. However, there is a little awareness of the minor CVOs among neuroimagers. This is the first study of contrast enhancement prevalence of the SF, OV, SC, and AP on brain MRI. All the latter are small, faint, rarely visualized, and therefore not likely to cause misinterpretation with significant sources of pathology that cause breakdown of the BBB, such as tumor or inflammation.